The past couple years I've done particularly well with "flash backs" and Quasis.... it's likely most everyone has tried them and had success feeling the added flash provides an edge.
Funny thing is that I have watched these flies drift past me to examine their profile as they drift down stream and they usually drift with the bead head down stream, tail up-stream with "the flash" side OPPOSITE the view of the fish (which are facing upstream).
Of course a great many fish first see the fly from one side or the other and "the flash" is likely somewhat visible from this angle.... but I believe they still see minimal flash most of the time until the fly is past them or starts to "hook" at the end of the drift...
To this end.... I have spent some time GOOGLING (very dangerous past-time that often causes me to start "surfing" until I find the "validation" to do things I might not otherwise do) and see that many "western" fly fishers are tying their nymphs with almost 100 percent flashy synthetics.
Well I now have a large "nymph box" near totally loaded with what the western guys call "flashies" in a variety of sizes, colors and seemingly crazy materials.
I had a bunch of synthetics from my salt water tying stuff and have added a bunch of new elements to those I saw on the googling adventure. On some of my "traditional" PT's I have incorporated a "twisted rope" made from four different colored strands of Krystal flash that I use over the PT abdomen in leiu of a copper or gold wire.... on many other flies the entire abdomen is made from this "dubbing rope". and the flash is now 360.... I think I "invented" this new technique! LOL
Boy have I had a lot of fun!
The only question that remains is whether or not "conservative" TN Bible Belt trout will eat a flashy like their western liberal California cousins?